Tank liner

ABSTRACT

A liquid-tight tank liner for use with elongate tanks with rounded end walls is disclosed. The liner is configured to carry the hydrostatic pressure loading which would otherwise be applied to longer side walls of the tank when the tank is filled with water or other liquid.

The present invention relates to a tank liner and more particularly to a liner for a tank for holding a liquid such as water, rainwater for example.

The present invention also relates to a tank, such as a water tank, that includes the liner.

Tanks for holding water, such as rainwater, in domestic and urban situations may, due to space limitations, need to be of a shape other than circular. For use where only confined space is available, a tank may be of an oblong or elongated shape with straight side walls and narrower end walls which are usually rounded, particularly when the tank is fabricated from corrugated steel panels. Tanks of this general shape require internal reinforcement to prevent the side walls from bowing outwardly under the hydrostatic pressure of the water stored within the tank.

For steel tanks, an approach which has been used is to install steel baffles between the two side walls, the baffles acting as ties to connect the two side walls and thereby to prevent them from distorting under load. The baffles are installed at the time of manufacture. The baffles are normally riveted to the side walls and care does need to be taken to ensure that the riveted connection is sealed against water leakage. Moreover a significant disadvantage with this construction is that the tank cannot be stored and transported in demounted condition to be assembled on site; accordingly significant storage and transportation costs can arise with tanks of this construction.

The present invention provides a liquid-tight tank liner for use with tanks of the general shape indicated above with the liner being configured to carry the hydrostatic pressure loading which would otherwise be applied to the longer side walls of the tank when the liner is filled with water or other liquid.

According to the present invention there is provided a liquid-tight liner for installation into a tank shell of elongate shape having opposed end walls and opposed side walls, the liner being fabricated from flexible sheet material impervious to passage of water or other liquid and the liner having a structure such that when the liner is installed within the tank shell and filled with liquid, the side walls of the tank shell will not be subject to substantial, if any, water or other liquid pressure tending to distort the side walls.

Typically, the opposed sides of the liner will only slightly contact or will be spaced inwardly from the side walls of the tank shell so that the side walls of the tank shell will not be subject to substantial, if any, water or other liquid pressure tending to distort the side walls.

The above-described liner, when installed in a tank shell and filled with water or other liquid is essentially self-supporting in the sense that it does not rely substantially, if at all, on the tank shell to structurally support the liner.

According to the present invention there is also provided a liquid-tight liner for installation into a tank shell of elongate shape having opposed end walls and opposed side walls, the liner being fabricated from flexible sheet material impervious to passage of water or other liquid, the liner providing a series of interconnected tubular cells extending from a base of a tank to the top of the tank shell, the configuration of the liner in its uninstalled state being such that when the liner is installed within the tank shell and is filled with water or other liquid, the cells at the respective ends of the liner will engage the adjacent end wall of the tank shell and will be deformed into a non-cylindrical shape, and the or each cell intermediate the end cells will be deformed into an elongate shape transversely of the side walls of the tank, the or each intermediate cell having part-cylindrical end walls which are positioned in relation to the side walls of the tank shell when in the installed state whereby the side walls of the tank shell will not be subject to substantial, if any, water or other liquid pressure tending to distort the side walls.

The cells may be fabricated as separate cells each with an upstanding wall and a base when installed in the tank shell, the adjacent cells being interconnected to provide water or liquid flow between the cells.

The liner may be constructed from panels of sheet material welded or glued together to form the cells such that adjacent cells share a common upstanding wall provided by a single panel and a base sealed to the lower ends of the panels forming the cells when installed in the tank shell. Advantageously, the connections are between parts of the panels directed transversely to the side walls of the tank shell whereby the connections are subject principally to a shear loading.

The liner may be constructed so that the upstanding wall and the base of each cell are separate components that are welded or glued or otherwise connected together. With such an arrangement, preferably the shape of the base is the shape required when the cell is installed in the tank shell and filled with water.

According to the invention there is also provided a liquid-tight liner for installation into a tank shell of elongate shape having opposed end walls and opposed side walls, the liner being fabricated from flexible sheet material impervious to passage of water or other liquid, the liner having an upstanding peripheral wall, a base sealed to the peripheral wall, and a series of spaced baffles extending between opposed sides of the peripheral wall lying adjacent the sides of the shell when the liner is installed in the tank shell, the sheet material forming the baffles being connected to the inside face of the peripheral wall by welding or gluing, and the baffles being of such a length that when the liner is installed in the tank shell and subject to the hydrostatic pressure of water or other liquid stored within the tank, the baffles will maintain the opposed sides of the liner in relation to adjacent sides of the tank shell whereby the side walls of the tank shell will not be subject to substantial, if any, water or other liquid pressure tending to distort the side walls.

According to the invention there is also provided a liquid-tight liner for installation into a tank shell of elongate shape having opposed end walls and opposed side walls, the liner being fabricated from flexible sheet material impervious to passage of water or other liquid, the liner providing a series of interconnected tubular cells and is such that when installed within the tank and filled with water or other liquid the side walls of the tank shell will not be subject to substantial, if any, water or other liquid pressure tending to distort the side walls.

The liner may be formed with water inlet and water outlet openings for when the liner is installed in a tank shell.

The liner may also be formed with fittings located in the openings to allow the liner to be coupled to water inlet and water outlet fittings when the liner is installed in a tank shell.

The liner may comprise clips or other members at an upper end of the liner that can hook onto a rim of a tank shell or otherwise connect the liner to the tank shell to facilitate hanging the liner in the tank shell in a desired orientation.

According to the invention there is also provided a liner as described above in a flat-packed form suitable for transport to an assembly site for a tank.

According to the invention there is also provided a tank for water or another liquid that includes a tank shell and the above-described liner installed in the tank shell, wherein the tank shell is an elongated shape with straight side walls and narrower end walls, wherein the liner has an upstanding wall which conforms approximately to the wall of the shell and a base sealed to the wall of the liner, and wherein opposite end wall sections of the wall of the liner are braced against the curved end walls of the shell and are thereby supported by the shell and whereby side wall sections of the wall of the liner can carry hydrostatic pressure loading of water or other liquid in the liner uniformly around the periphery of the cells without subjecting the side walls of the shell to substantial, if any, loading tending to cause the side walls to distort.

Preferably the liner comprises a series of separate cells having cylindrical upstanding walls that can carry hydrostatic pressure loading of water or other liquid in the liner uniformly around the periphery of the cells without subjecting the side walls of the shell to substantial, if any, loading tending to cause the side walls to distort.

Preferably the end cells of the series of cells are braced against the end walls of the shell and cause intermediate cells in the series of cells to be compressed so that the cells are elongated transversely to a longitudinal axis of the shell.

The end walls of the shell may be any suitable shape. Suitable shapes include part-cylindrical and squared.

Typically, the cells are interconnected at their upper and lower ends to permit water flow between the series of cells.

Typically, the tank shell is fabricated from corrugated steel panels.

The invention will now be further described with reference to the accompanying drawings, in which:

FIG. 1 shows schematically a plan view of a liner with baffles installed within a tank shell;

FIG. 1A shows a detail of FIG. 1;

FIG. 2 is a schematic plan view showing a liner consisting of cylindrical cells installed with the tank shell;

FIG. 3 is a schematic plan view to illustrate the underlying concept of liners in accordance with particularly preferred embodiments of the invention;

FIGS. 4 to 6 are schematic plan views of different forms of liner in accordance with preferred embodiments of the invention;

FIG. 7 shows schematically a detail of a liner in accordance with a further embodiment of the invention;

FIG. 8 is a view similar to FIG. 7 showing a modified arrangement;

FIG. 9 is a schematic plan view of yet a further embodiment of the invention; and

FIG. 10 is a schematic vertical section of yet another embodiment of the invention.

FIG. 1 shows a tank having an outer shell 2 of steel or other suitable material of the general shape just discussed. The tank shell 2 is lined by a liquid-tight liner 4 fabricated from flexible sheet material impervious to water or other liquid. The liner consists of a peripheral or upstanding wall which conforms approximately to the wall of the shell, and a base sealed relative to the peripheral wall. Baffles 6 of the same or similar flexible material extend between the two longer sides of the liner wall and act as ties between the longer sides, so the baffles perform a similar purpose to the steel baffles previously discussed but instead act to restrict the outward deformation of the sides of the liner when under hydrostatic pressure load. Accordingly, the opposite sides of the tank shell 2 will not be subject to loading tending to cause them to deform outwardly under load. It will be seen that the effect of the baffles 6 is to provide a scalloped shaping at the sides of the liner, the scallop shape being defined by a series of cusps 8 interconnected by portions 10 of relatively large radius. The connection between each end of the baffle 6 and the adjacent face of the liner is a welded connection, details of which are shown in FIG. 1A. It will be seen that one face of the baffle 6 at its end portion is welded to the inside face of the liner at one side of the cusp 8 which is created by the baffle, and a reinforcing strip 12 of the same plastics material is welded to the other face of the baffle 6 and the inside face of the liner at the opposite side of that cusp.

In principle, this provides a solution to the problems discussed at the outset as the tank shell itself does not require to be constructed with side walls which are reinforced to carry the hydrostatic pressure loading. It is noted that the arrangement can include contact between the liner 4 and side walls of the tank shell 2, provided the contact is such that a substantial part of the hydrostatic pressure loading is carried by the liner. The tank can therefore be transported in prefabricated sections assembled on site. The liner is fabricated from flexible sheet plastics material which is folded into a compact flat pack form for transportation and is then fitted into the outer shell. However, with the configuration shown in FIG. 1, when the liner is under load due to hydrostatic pressure, the welded connections between the end of the baffle 6 and reinforcing strip 12 and the inside face of the liner are under a tensile load and may be susceptible to failure by the welds tending to peel outwardly from the cusp of the liner if the welds are not properly made. It is, however, to be understood that this construction is viable in some circumstances.

FIG. 2 shows an alternative in which the liner is constructed from a series of separate cylindrical cells 20 of a diameter slightly less than the width of the tank shell 2 whereby each cell will, as a result of its shape, carry the hydrostatic pressure loading uniformly around its periphery without subjecting the side walls of the shell to substantial, if any, loading which tends to cause them to deform. The cells 20 are interconnected at their upper and lower ends to permit liquid flow between the series of cells. Although from a structural standpoint this provides a solution to the problem of using the liner itself to carry the hydrostatic pressure loading, nevertheless it results in a significant amount of unused tank space which could represent up to 25% of the overall volume of the shell and, as such, while this has utility it is not a particularly preferred option of the invention.

FIG. 3 shows the basic configuration of preferred embodiments of the invention. This configuration can be achieved with a number of alternative constructions as will be described subsequently, but first the basic configuration itself will be described. The configuration consists of a cell 30 at each end of the liner and which is supported against the adjacent curved end of the shell 2, and one or more intermediate cells 32 between the end cells 30. As shown, there are three intermediate cells 32 but there may be more than or less than three intermediate cells 32 depending on the overall length of the tank shell. The configuration of the liner is such that when the liner is installed and filled with water or other liquid and under hydrostatic pressure loading, the end cells 30 will be braced against the curved end walls of the shell and will cause the intermediate cells 32 to be compressed into the general shape illustrated in which the cell is elongated transversely to the longitudinal axis of the shell. The engagement of the end cells 30 with the rounded ends of the tank shell will result in some of the hydrostatic pressure loading being taken by the rounded ends and as will be understood, by reason of their shape they are inherently able to take that loading without deformation. This arrangement is essentially self-supporting.

Although it will be seen that the overall peripheral shape of the liner is broadly similar to that shown in FIG. 1 the rounded ends of each cell 32 are deformed to a smaller radius than that shown in FIG. 1. This reduction in radius, which also occurs in the portion of the end cells 30 adjacent the next intermediate cell 32, results in a reduction in the skin tension of the liner when under load which provides constructional advantages as will be described. Moreover, the resulting radius reduction reduces the amount of unusable or wasted space within the tank shell as may be seen by comparing the configuration of FIG. 3 with that of FIG. 2.

FIG. 4 shows a practical embodiment of the present invention utilizing the concept. The liner is formed from a series of separate cells 30, 32 each closed at the base and possibly also at the top. The peripheral wall of each cell is formed by fabricating sheet material into tubular form and then welding that to a base. A separate base may be provided for each cell or alternatively the cells may be welded to a common base. A separate base for each cell has advantages in terms of facilitating packing and transporting the liner as a compact flat-pack. This is an important consideration. The shape of each base is selected to be the shape required for the base when the cell is installed in the tank shell and filled with water. The base and the peripheral wall of each cell can be connected together by any suitable means. One particularly suitable option is to heat weld the components together where the components are formed from suitable materials. In addition, forming the separate base for each cell from a rigid of semi-rigid material has advantages in terms of installing the liner in a correct position in the tank shell initially and thereafter maintaining the liner in the correct position over time as the liner changes shape as water is supplied into and is discharged from the tank. In this regard, the applicant has found that maintaining the liner in position in the tank shell is an important consideration. In addition, forming the separate base for each cell from a rigid or semi-rigid material is advantageous in allowing easier replacement of a liner. Instead of closing the cells by a base, the cells can be closed at the bottom by welding together their lower edges. The adjacent cells of the liner are connected by sealed ports at least at their lower ends to permit liquid flow between the cells. The circumferential size of each of the intermediate cells 32 is less than that of the two end cells 30 (but may alternatively be the same as the end cells) and the sizes of the cells 30, 32 in relation to the size of the tank shell is such that with the liner placed within the tank shell and filled with liquid, the configuration shown in FIG. 3 will be obtained. The liner also comprises clips (not shown) or other suitable members at upper ends of the walls of the cells that are formed to hook over the rim of the tank shell or otherwise connect the liner to the tank shell to facilitate hanging the liner in a selected orientation within the tank shell. The use of this clip assembly avoids the liner collapsing to the bottom of the tank when the liner is empty. This is an important consideration given that the liner will hold different amounts of water over time. The liner is also advantageously formed with water inlet and water outlet openings, and appropriate fittings for connecting water inlet and outlet assemblies to the liner when the liner is installed in a tank shell are connected to the inlet/outlet openings. It can be appreciated that the liner, so formed, can be conveniently transported to an installation site and unfolded and positioned in a tank shell.

Instead of forming the liner from a series of separate tubular cells which are then assembled together in the manner shown in FIG. 4, adjacent cells may be constructed from separate panels of sheet material welded together so that a single panel forms a wall common to two adjacent cells, that wall being a substantially straight wall extending transverse to the side wall of the tank shell. Alternative arrangements for achieving this are shown in FIGS. 5 and 6. In these figures, the individual panels are designated 40 a to 40 e, the zones of the welded connections between the panels are designated 42, and the transverse walls common to adjacent cells are designated 44. With this configuration, the adjacent panels forming the liner are welded in the zone of the common transverse walls 44 and as a result when the liner is under load the welded connection will tend to be in shear loading in the plane of the common wall. Welded connections of this type have a stronger resistance to loading in shear in the plane of the joint than in tension transverse to the plane of the joint as occurs with the arrangement discussed with reference to FIG. 1 and which may be susceptible to failure by peeling. Moreover, as discussed earlier, the tighter radius achieved by the opposite end walls of the cells in the compressed configuration illustrated reduces skin tension whereby the loading acting on the welded connection is reduced. As a result, with each of the configurations illustrated in FIGS. 5 and 6 a strong, reliable, welded connection can be achieved between the panels forming the individual cells.

The cells formed by the assembled panels are closed at the bottom by a base layer of sheet material welded to the panels. To provide intercommunication between the cells, the individual panels in the zone of the walls 44 common to two adjacent cells may remain unsealed to the base panel to permit passage of water, and the lower edge of the panel in this zone may be profiled to provide a large area flow port.

Instead of forming the liner with a series of individual cells, the peripheral configuration of the liner with a scalloped shape of tight radius as shown in FIG. 3 can be induced by welding baffles between the opposed sides of the liner. See FIG. 7. The difference between this and the configuration shown in FIGS. 1 and 1A is that the tighter radius allows the baffle 6 now to be welded to a part of the liner wall which is directed transversely to the side wall of the shell so that the welded connection is now under a shear loading rather than the tensile loading subject to failure by peeling inherent in the configuration of FIGS. 1 and 1A. As previously discussed, the tighter radius also results in a reduction in skin tension and a consequent reduction in the loading applied to the welded connection. In the configuration shown in FIG. 7 the end of the baffle 6 is welded to the internal face of the liner at one side of the cusp 8, and at the other side of the cusp 8 a reinforcing strip 12 of the same material is welded to the other side of the baffle and the internal face of the liner. In the modified configuration shown in FIG. 8, the end of the baffle 6 is welded through the two layers which define the cusp 8 thereby bonding the two layers and avoiding the need for the reinforcing strip present in FIG. 7.

FIG. 9 shows a variant of a scalloped shape induced by welding baffles between the opposed sides of the liner and, in effect, represents an intermediate configuration between that shown in FIG. 1 and that shown in FIG. 3. In the configuration of FIG. 9, the scalloped shape is to a tighter radius than that shown in

FIG. 1 but larger than that shown in FIG. 3 whereby the skin tension will be reduced in relation to that of the configuration of FIG. 1 but greater than that of the configuration in FIG. 3. Moreover, the tighter radius in relation to that of FIG. 1 increases the shear component of the loading of the welded connection between the baffles and the opposed sides of the liner and thereby reduces the peel loading. Although the loading of the welded connection is not principally in shear as occurs with some of the other embodiments, nevertheless the shear component of the loading in conjunction with the reduced skin tension resulting from the increased radius should provide a more durable connection than that which arises in the configuration of FIG. 1. At the ends, more of the hydrostatic pressure loading is taken by the liner due to the increased skin tension whereby the loading carried by the end walls of the shell will be reduced in relation to that of FIG. 3. It is also to be noted that the Configuration of FIG. 9 with the increased radius of the scalloped shape in relation to that of FIG. 3 provides somewhat less unusable space within the shell.

FIG. 10 shows an embodiment in which the baffles 6 extend horizontally in the lengthwise direction of the liner and are vertically spaced. The baffles extend along the length of the opposite sides of the liner and possibly also into part of the end zones of the liner and provide a scalloped shaping in vertical cross-section as is clearly shown in FIG. 10. Preferably, and as shown, the baffle spacing reduces towards the bottom of the liner and the scallop curvature becomes tighter towards the bottom and this maintains an even skin tension along the height of the liner despite the increasing pressure towards the bottom. The liner is supported from the shell by suspending from the top of the shell, and fabric panels or straps 50 extending vertically are secured to the external faces of the cells to maintain them at the correct height when the liner is empty. The liner may be open or closed at the top. A variant of the configuration shown in FIG. 10 can be produced by a series of separate, but interconnected, tubular cells arranged with their axes extending substantially horizontally.

Although reference has been made herein to welded connections between various components forming the liner, the connections may alternatively be glued connections and to an extent this will be determined by the nature of the fabric used.

In all embodiments of the invention the walls of the liner and the baffles (if present) are fabricated from flexible sheet material of appropriate characteristics to ensure it has sufficient strength to withstand the hydrostatic pressure loading to which it will be subjected in use. The fabric must be able to support tension loads over a prolonged period of time without stretching while having resistance to abrasion and to temperature to withstand solar heating via the shell of portions of the liner above water level. Suitable materials may be composed of a scrim or woven fabric having an impervious coating on one or both sides and such materials are already commonly used for tarpaulins and tank liners of other types. In situations where the tank is to be used for storing water, the impervious coating should be a food grade quality material.

When a base is used to close the cells, as it is not subject to the same tension loading as the walls and baffles, it may not necessarily need to be fabricated from the same material as the walls of the liner. Similar considerations apply for a top closure (if present) at the upper ends of the cells. The base may alternatively be of a semi-rigid material and which may be cut to the same shape as the shell, thereby making it easy to drop the liner into the shell and self-locate, as described above in relation to the FIG. 4 embodiment.

Although the preferred embodiments have been described with reference to a liner for an elongate tank shell having rounded ends, a liner in accordance with the broad principles of the invention could also be fabricated for use with an elongate shell having squared or any other shaped ends provided that the ends are of a size and/or construction such that they will not deform outwardly when subject to hydrostatic pressure loading.

In addition, although the preferred embodiments have been described with reference to a tank shell formed from corrugate steel, the invention also extends to tank shells formed from other materials.

The embodiments have been described by way of example only and modifications are possible within the scope of the invention.

Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers. 

1. A liquid-tight liner for installation into a tank shell of elongate shape having opposed end walls and opposed side walls, the liner being fabricated from flexible sheet material impervious to passage of water or other liquid, the liner providing a series of interconnected tubular cells extending from a base of the tank to a top of the tank shell, the configuration of the liner in its uninstalled state being such that when the liner is installed within the tank shell and is filled with water or other liquid, the cells at the respective ends of the liner will engage the adjacent end wall of the tank shell and will be deformed into a non-cylindrical shape, and the or each cell intermediate the end cells will be deformed into an elongate shape transversely of the side walls of the tank, the or each intermediate cell having part-cylindrical end walls which are positioned in relation to the side walls of the tank shell when in the installed state whereby the side walls of the tank shell will not be subject to substantial, if any, water or other liquid pressure tending to distort the side walls.
 2. A liner according to claim 1 designed for use with a tank shell in which the end walls of the tank shell are of part-cylindrical shape.
 3. A liner according to claim 1, wherein the cells are fabricated as separate cells each with an upstanding wall and a base when installed in the tank shell, each cell being interconnected to an adjacent cell to provide water or other liquid flow between the cells.
 4. A liner according to claim 1, wherein the liner is constructed from panels of the sheet material welded or glued together to form the cells such that adjacent cells share a common upstanding wall provided by a single panel and a base sealed to the lower ends of the panels forming the cells when installed in the tank shell.
 5. A liner according to claim 4, wherein the welds connecting the adjacent panels are between parts of the panels directed transversely to the side walls of the tank shell when the liner is installed in the tank whereby the welded or glued connections are subject principally to a shear loading when water or other liquid is in the liner.
 6. A liner according to claim 5, wherein the upstanding wall and the base of each cell are separate components that are welded or glued or otherwise connected together.
 7. A liner according to claim 6, wherein the shape of the base is the shape required when the cell is installed in the tank shell and filled with water.
 8. A liner according to claim 1 formed with water inlet and water outlet openings for when the liner is installed in a tank shell.
 9. A liner according to claim 8 formed with fittings located in the openings to allow the liner to be coupled to water inlet and water outlet fittings when the liner is installed in a tank shell.
 10. A liquid-tight liner for installation into a tank shell of elongate shape having opposed end walls and opposed side walls, the liner being fabricated from flexible sheet material impervious to passage of water or other liquid, the liner having an upstanding peripheral wall, a base sealed to the peripheral wall, and a series of spaced baffles extending between opposed sides of the peripheral wall lying adjacent the sides of the shell when the liner is installed in the tank shell, the sheet material forming the baffles being connected to the inside face of the peripheral wall by welding or gluing, and the baffles being of such a length that when the liner is installed in the tank shell and subject to the hydrostatic pressure of water or other liquid stored within the tank, the baffles will maintain the opposed sides of the liner in relation to adjacent sides of the tank shell whereby the side walls of the tank shell will not be subject to substantial, if any, water or other liquid pressure tending to distort the side walls.
 11. A liner according to claim 10, wherein the part of the inside face of the peripheral wall to which each baffle is connected is directed transversely to the side walls of the tank shell when the liner is installed in the tank whereby the connections are subject principally to a shear loading when water or other liquid is in the liner.
 12. A liner according to claim 10, wherein the baffles are spaced longitudinally of the liner.
 13. A liner according to claim 10, wherein the baffles are spaced vertically of the liner.
 14. A liner according to claim 10, wherein the opposite ends of the liner when installed in the tank are engaged with the ends of the tank shell.
 15. A liquid-tight liner for installation into a tank shell of elongate shape having opposed end walls and opposed side walls, the liner being fabricated from flexible sheet material impervious to passage of water or other liquid, the liner providing a series of interconnected tubular cells and is such that when installed within the tank and filled with water or other liquid the side walls of the tank shell will not be subject to substantial, if any, water or other liquid pressure tending to distort the side walls.
 16. A liner according to claim 15, wherein the cells are fabricated as separate cells, each cell being interconnected to an adjacent cell to provide liquid flow between the cells.
 17. A liner according to claim 15, wherein the cells are directed in the liner with the axis of each cell extending substantially vertically.
 18. A liner according to claim 15, wherein the cells are directed in the liner with the axis of each cell extending substantially horizontally.
 19. A liquid-tight liner for installation into a tank shell of elongate shape having opposed end walls and opposed side walls, the liner being fabricated from flexible sheet material impervious to passage of water or other liquid and the liner having a structure such that when the liner is installed within the tank shell and filled with liquid the side walls of the tank shell will not be subject to substantial, if any, water or other liquid pressure tending to distort the side walls.
 20. A tank for water or another liquid that comprises a tank shell and a liner according to any one of the preceding claims installed in the tank shell, wherein the tank shell is an elongated shape with straight side walls and narrower end walls, wherein the liner has an upstanding wall which conforms approximately to the wall of the shell and a base sealed to the all of the liner, and wherein opposite end wall sections of the wall of the liner are braced against the end walls of the shell and are thereby supported by the shell and whereby side wall sections of the wall of the liner can carry hydrostatic pressure loading of water or other liquid in the liner around the periphery of the cells without subjecting the side walls of the shell to substantial, if any, loading tending to cause the side walls to distort.
 21. A tank according to claim 20, wherein the liner comprises a series of separate cells having cylindrical upstanding walls that can carry hydrostatic pressure loading of water or other liquid in the liner uniformly around the periphery of the cells without subjecting the side walls of the shell to substantial, if any, loading tending to cause the side walls to distort.
 22. A tank according to claim 21, wherein the end cells of the series of cells are braced against the end walls of the shell and cause intermediate cells in the series of cells to be compressed so that the cells are elongated transversely to a longitudinal axis of the shell. 